This invention relates to circuit breakers, and, more particularly, to a motor control center circuit breaker assembly.
Motor control centers, such as described in U.S. Pat. No. 5,424,911 entitled Compact Motor Controller Assembly, contain several components related to electric motor operation such as electric contactors, circuit breakers, power supply transformers, disconnect switches and the like.
An electric disconnect switch is described in U.S. Pat. No. 4,785,145 entitled Modular Electrical Disconnect Switch, and one such circuit breaker is described in U.S. Pat. No. 4,884,164 entitled Molded Case Circuit Interrupter. The use of a circuit breaker for both motor protection and switch functions is described in U.S. Pat. No. 4,945,450 entitled Modular Electric Switch-Circuit Breaker Assembly. A unit combining both circuit breaker and contactor functions is found in U.S. Pat. No. 5,657,193 entitled Electronic Control Module for Motor Controller Units.
It is frequently necessary to ensure that electrical equipment cannot be operated, for example while maintenance work is being carried out. It is essential to ensure that circuit breakers associated with the electrical equipment are secured in the OFF position to avoid inadvertent operation that can lead to unplanned exposure of personnel or equipment.
Also, it is often necessary to ensure that the electrical equipment is secured in the ON position, to prevent accidental shutdown of machinery, such as refrigeration equipment, life support systems, fire protection devices and continuous processes which require 1-2 days to start (e.g. cement manufacturing). Therefore, the ability to lock the circuit breaker in either the OFF position or the ON position is desirable.
When a circuit breaker is used with motor control units (centers) as an electric disconnect switch, it is important that the operating handle be locked in the OFF position mechanically so that the operating handle cannot be moved to the ON position. It is also important to ensure that the prior to locking the operating handle in the OFF position, the operating handle is in the true or positive OFF position. It may also desirable to lock the operating handle in the ON position.
The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by a locking device for use of an electric disconnect switch having a handle operator assembly. In an exemplary embodiment of the invention, a locking device for use on an electric disconnect switch having a handle operator assembly including a slide plate slidably positioned within the housing and a first lock arranged to engage said slide plate and secure the handle operator assembly in an engaged position.